I have two tricks for better movement, add the following to your .vimrc:
" for scrolling up and down quickly
nnoremap J 7j
nnoremap K 7k
vnoremap J 7j
vnoremap K 7k
and the second (which requires a third party plugin):
" easymotion allows us to jump to all places that could have been reached by
" (w in this case), and the bd- indicates we want to search backwards too.
nmap f <Plug>(easymotion-bd-w)
vmap f <Plug>(easymotion-bd-w)
The first one originates from recognizing the problem from the antipatterns article: that spamming j j j j to get down to the line you want is dumb. But I choose not to follow the advice of most vim articles I read which is to learn built-in tricks such as typing 10j or :<line number>. The milliseconds it takes for me to count the number of lines I want to go down or assess the line number of the line I'm interested in aren't worth it, I'll just tap j if the line is close enough or J if it is five or more lines down. I think it is a good solution.
The even better solution (and I use them both in tandem) is to install easymotion [1] and use it like I show in the second example.
I also use gg and G to get to leap to the top and bottom of the file quite a lot.
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As to your question about using O to insert above the current line, that should not work that way. Your specific issue sounds very much like a binding has been defined for O<other character>. Type :nmap in vim to display a list of bindings and check for lines starting with O. It might be in your .vimrc or some plugin defined something. I would definitely say remove the binding or the plugin rather than put up with that, O is very useful.
[1] https://github.com/easymotion/vim-easymotion
The even better solution (and I use them both in tandem) is to install easymotion [1] and use it like I show in the second example.
I also use gg and G to get to leap to the top and bottom of the file quite a lot.
---
As to your question about using O to insert above the current line, that should not work that way. Your specific issue sounds very much like a binding has been defined for O<other character>. Type :nmap in vim to display a list of bindings and check for lines starting with O. It might be in your .vimrc or some plugin defined something. I would definitely say remove the binding or the plugin rather than put up with that, O is very useful.
[1] https://github.com/easymotion/vim-easymotion